The origins and volumes of waters which mass-transport silica in sedimentary basins remain obscure. Many previous analytical studies have illustrated cases where quartz cements in sandstones originate from complex and variable fluids. By contrast we show, by using a combination of separation and analytical techniques, that in lower Permian sandstones of the southern North Sea the cementing fluid was isotopically uniform during growth of quartz cement with a 6l80 of 19.6 2 l.O%o V-SMOW. In this relatively uniform fluid quartz cements grew and developed complex cathodoluminescence (CL) zonations. Petrographic data show that 8-1Ooh quartz cement (locally 30%) was imported into this 380 km'x180 m thick aeolian sandstone, and cement distribution controlled by depositional permeabilities. We infer a large-scale, high volume, flux of evolved meteoric fluid during 2 km deep burial, and show that complex CL zonation may arise from relatively subtle changes in water composition.